1. Field of the Disclosed Embodiments
This disclosure relates to systems and methods for determining a position of a vehicle traversing a constrained path via environmental information from, and collected by, communications equipment installed both at fixed points along a known route and onboard the traveling constrained path vehicle and communications established between the fixed and moving components of the system.
2. Related Art
Various techniques exist for localizing positions of moving vehicles and other moving objects/bodies. Among these techniques are the increasing uses of handheld, or vehicle mounted position keeping devices, and/or implementation of automatic vehicle locators (AVLs). An AVL system, for example, generally includes Global Positioning System (GPS) locators mounted on, for example, the tops of individual vehicles, including busses and trains. The individual locator components provide inputs to a local communication network, such as a cellular, Wi-Fi or other like network that provides adequate communication coverage. In this manner, positional information signals are generated by the AVL GPS system on or in the individual vehicles that are in turn transmitted to some central location (back-office) to centrally track vehicle locations generally at all times.
AVL systems are more commonly adapted to busses, which more generally operate in an open-air GPS-accessible environment than do, for example, trains. Coincidentally, there is generally understood to be a greater need for individual tracking of busses over trains in that trains (1) are generally much more constrained with regard to their movement i.e. on their tracks, and (2) are generally considered to be most often operating “on [or nearly on] schedule.”
GPS-centric AVL systems are well known, but these systems tend to be proprietary to particular vendors. These AVL systems also may not be particularly adaptable to trains based on an amount of time that a train may spend out of an environment in which GPS localization is available.
Those of skill in the art also recognize that GPS localization, cellular (3 point) localization and other typical forms of individual, vehicle, or unit localization, require significant computing overhead based on a need to resolve a location of the individual, vehicle or unit in three axes (latitude, longitude and altitude/height).
Typically, because trains and other constrained-path vehicles are limited in their freedom of movement, advanced technology systems for resolving positions of the trains and/or other constrained-path vehicles may be considered wasteful, i.e., not cost effective based on the need for extensive supporting computer overhead. This is the reason why, particularly for trains, locating systems tend to be based on much more “low-technology” solutions. Any number of conventional methods may be used to localize a position, or a track occupancy, of a vehicle, particularly a train, when constrained to physical movement along a specified track.
The low-tech solutions for position monitoring of trains include axle counters at a beginning and an end of a particular track section. Information from the track axle counters may be transmitted to a central control location that maintains often a dynamic visual overview specifying a status of a section of track as occupied or non-occupied. Comparison is made between the number of axles in and the number of axles out of the particular section to confirm occupancy or non-occupancy. Track wayside control (TWC) loops are also or otherwise used to provide essentially the same information to the central control location for other sections of track. These are magnetized loops that detect a train in proximity or passing across those loops. Shunting is also used is in certain circumstances and is a mechanism by which a small electrical current is run through one track in a particular section and grounded to the other track through the metal wheels and axles. This shunting can be detected as the occupancy metric and forwarded to the central control location as well. Such redundant systems are emplaced and their use is warranted to ensure safety, which is paramount.